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FLUE TEMPERATURE PROBE NTC AND SAFETY THERMAL FUSE
20 FLUE TEMPERATURE PROBE NTC AND
SAFETY THERMAL FUSE
20.1 Function
The Flue temperature probe NTC A in Figure 20.1 and Figure
20.2 senses the temperature of the combustion products that
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B
A
Figure 20.1
If the temperature of the combustion products circuit reaches the
limit temperature, the Flue temperature probe NTC reduces the
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products should decrease to a safe value temperature.
In the case that the temperature of the combustion products
reaches a potentially dangerous value, it stops the boiler opera-
tion (lock-out).
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and bends.
The use of kits different from the original isn't however allowed,
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A
C
Figure 20.2
A Safety thermal fuse B in Figure 20.1 - Figure 20.2 is also con-
nected in series with the Flue temperature probe NTC and acts
as a safety device in extreme case of incorrect operation of the
Flue temperature control system.
Reaching the breakdown temperature it opens the circuit and
locks out the boiler.
In case of intervention of this safety device the heat exchanger (part
shown in Figure 20.3) may be damaged and must be replaced.
Figure 20.3
20.2 Removal
1 Remove all the case panels.
2 Disconnect the connector C from the Flue temperature probe
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4 Assemble the Flue temperature probe NTC carrying out the
20.3 Checks
1 Set the temperature control knobs to their max. position and
2 Allow the boiler to reach its maximum operating temperature
B
1 Remove the Flue temperature probe NTC (see section 20.2).
2 Measure the Flue temperature probe NTC electrical resist-
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
NTC by pressing the plastic hook placed on the side of the
connector.
20.2) from the condensing heat exchanger.
removal operations in reverse sequence.
Overheat temperature value
run the boiler in d.h.w. and c.h.
(monitor the temperature gauge on the instrument panel).
The boiler should maintain a temperature below that of the
Flue temperature probe NTC and no overheat intervention
should occur.
Temperature-resistance relationship.
ance at the ambient temperature and check it according to
the graph in (Figure 20.4)
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